Ultrasensitive aptasensor based on graphene-3,4,9,10-perylenetetracarboxylic dianhydride as platform and functionalized hollow PtCo nanochains as enhancers

A novel electrochemical aptasensor for ultrasensitive detection of thrombin is described that uses the conductive graphene-3,4,9,10-perylenetetracarboxylic dianhydride nanocomposites (GPA) as desirable sensor platform and hollow PtCo nanochains–thionine–Pt–HRP labeled secondary thrombin aptamer (HPtCoNCs–Thi–Pt–HRP–TBA, aptamer II) for signal amplification. With the surface area enhanced by GPA nanocomposites, the amount of immobilized primary thrombin aptamer can be improved. More importantly, the synthesized HPtCoNCs also yielded large surface area, which provide substantial binding sites for thionine–Pt–HRP–TBA. The thionine acts as a mediator of electron transfer between HRP and electrode surface. Enhanced sensitivity was achieved by introducing the multibioconjugates of aptamer II onto the electrode surface through “sandwich” reactions. With amplifying factors mentioned above, a wider linear range from 10−15 to 10−9 M was acquired with an ultralow detection limit of 6.5 × 10−16 M for thrombin. This amplification strategy showed acceptable stability and reproducibility, high sensitivity, and good precision, which could provide a promising potential for clinical screening and point-of-care diagnostics.